Combined semiconductor apparatus and a fabricating method thereof

ABSTRACT

A semiconductor apparatus includes two thin semiconductor films bonded to a substrate, and a thin-film interconnecting line electrically connecting a semiconductor device in the first thin semiconductor film to an integrated circuit in the second thin semiconductor film. The two thin semiconductor films are formed separately from the substrate. The first thin semiconductor film may include an array of semiconductor devices. The first and second thin semiconductor films may be replicated as arrays bonded to the same substrate.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a semiconductor apparatus useful in,for example, a light-emitting diode (LED) print head in anelectrophotographic printer.

2. Description of the Related Art

Referring to FIG. 28, a conventional LED print head 900 includes acircuit board 901 on which are mounted a plurality of LED array chips902 having electrode pads 903, and a plurality of driving integratedcircuit (IC) chips 904 having electrode pads 905. The electrode pads903, 905 are interconnected by bonding wires 906 through which currentis supplied from the driving IC chips 904 to LEDs 907 formed in the LEDarray chips 902. Further electrode pads 909 on the driving IC chips 904are connected to bonding pads 910 on the circuit board 901 by furtherbonding wires 911.

For reliable wire bonding, the electrode pads 903, 905, 909 must becomparatively large, e.g., one hundred micrometers square (100 μm×100μm), and the LED array chips 902 must have approximately the samethickness as the driving IC chips 904 (typically 250-300 μm), eventhough the functional parts of the LED array chips 902 (the LEDs 907)have a depth of only about 5 μm from the surface. To accommodate theneeds of wire bonding, an LED array chip 902 must therefore be muchlarger and thicker than necessary simply to accommodate the LEDs 907.These requirements drive up the size and material cost of the LED arraychips 902.

As shown in plan view in FIG. 29, the electrode pads 903 may need to bearranged in a staggered formation on each LED array chip 902. Thisarrangement further increases the chip area and, by increasing thelength of the path from some of the LEDs 907 to their electrode pads903, increases the associated voltage drop.

The size of the driving IC chips 904 also has to be increased toaccommodate the large number of bonding pads 905 by which they areinterconnected to the LED array chips 902.

Light-emitting elements having a thin-film structure are disclosed inJapanese Patent Laid-Open Publication No. 10-063807 (FIGS. 3-6, FIG. 8,and paragraph 0021), but these light-emitting elements have electrodepads for solder bumps through which current is supplied. An array ofsuch light-emitting elements would occupy substantially the same area asa conventional LED array chip 902.

SUMMARY OF THE INVENTION

A general object of the present invention is to reduce the size andmaterial cost of semiconductor apparatus.

A more specific object is to reduce the size and material cost of asemiconductor apparatus comprising an array of light-emitting elementsand their driving circuits.

The invention provides an integrated semiconductor apparatus in which apair of thin semiconductor films are formed separately from, then bondedto, a substrate. The first thin semiconductor film includes at least onesemiconductor device. The second thin semiconductor film includes anintegrated circuit and a terminal to drive the semiconductor device inthe first semiconductor film. An individual interconnecting line extendsfrom the first thin semiconductor film to the second thin semiconductorfilm, partly crossing the substrate and electrically connecting thesemiconductor device in the first thin semiconductor film to theterminal in the second thin semiconductor film. If necessary, adielectric film may be provided to insulate the individualinterconnecting line from parts of the thin semiconductor films and fromthe substrate.

The semiconductor device in the first thin semiconductor film may be anLED. The thin semiconductor film may include an array of LEDs which aredriven by the integrated circuit in the second thin semiconductor film.Compared with conventional semiconductor apparatus comprising an LEDarray chip and a separate driving IC chip, the invented semiconductorapparatus has a reduced material cost because the LED array andintegrated circuit are reduced to thin films and the overall size of theapparatus is reduced. The overall size is reduced because the large wirebonding pads conventionally used to interconnect the LEDs and theirdriving circuits are eliminated, and because the distance between theLEDs and their driving circuits can be reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

In the attached drawings:

FIG. 1 is a perspective view schematically showing part of an integratedLED/driving-IC chip according to a first embodiment of the invention;

FIG. 2 is a plan view schematically showing the integratedLED/driving-IC chip in FIG. 1;

FIG. 3 is a more detailed plan view schematically showing part of theintegrated LED/driving-IC chip in FIG. 1;

FIG. 4 is a cross sectional view schematically showing a cross sectionthrough line S₄-S₄ in FIG. 3;

FIG. 5 is a plan view of a semiconductor wafer on which integratedLED/driving-IC chips are fabricated according to the first embodiment ofthe invention;

FIGS. 6A through 6E are plan views schematically showing steps in thefabrication process for the integrated LED/driving-IC chip in FIG. 1;

FIG. 7 is a cross sectional view schematically showing a first stage inan LED epitaxial-film fabrication process;

FIG. 8 is a cross sectional view schematically showing a second stage inthe LED epitaxial-film fabrication process;

FIG. 9 is a cross sectional view schematically showing a third stage inthe LED epitaxial-film fabrication process;

FIG. 10 is a cross sectional view schematically showing a cross sectionthrough line S₉-S₉ in FIG. 9;

FIGS. 11A, 11B, and 11C are cross sectional views schematically showingsteps in a fabrication process for the thin integrated circuit film inFIG. 1;

FIG. 12 is a plan view schematically showing part of an integratedLED/driving-IC chip according to a second embodiment of the invention;

FIG. 13 is a plan view schematically showing part of an integratedLED/driving-IC chip according to a third embodiment;

FIG. 14 is a cross sectional view schematically showing a cross sectionthrough line S₁₄-S₁₄ in FIG. 13;

FIG. 15 is a plan view schematically showing part of an integratedLED/driving-IC chip according to a fourth embodiment of the invention;

FIG. 16 is a perspective view schematically showing part of theintegrated LED/driving-IC chip in FIG. 15;

FIG. 17 is a cross sectional view schematically showing a cross sectionthrough line S₁₇-S₁₇ in FIG. 15;

FIG. 18 is a perspective view schematically showing part of anintegrated LED/driving-IC chip according to a fifth embodiment of theinvention;

FIG. 19 is a plan view schematically showing part of the integratedLED/driving-IC chip in FIG. 18;

FIG. 20 is a plan view schematically showing part of an integratedLED/driving-IC chip according to a sixth embodiment of the invention;

FIG. 21 is a plan view schematically showing part of an integratedLED/driving-IC chip according to a seventh embodiment;

FIG. 22 is a plan view schematically showing part an integratedLED/driving-IC chip according to an eighth embodiment;

FIG. 23 is a perspective view schematically showing part of theintegrated LED/driving-IC chip in FIG. 22;

FIG. 24 is a plan view illustrating the fabrication of the thinintegrated circuit film in the eighth embodiment;

FIG. 25 is a plan view schematically showing an integratedLED/driving-IC chip according to a ninth embodiment of the invention;

FIG. 26 is a cross sectional view schematically showing an LED printhead employing the invented semiconductor apparatus;

FIG. 27 is a schematic cutaway side view of an LED printer employing theinvented semiconductor apparatus;

FIG. 28 is a perspective view schematically showing part of aconventional LED print head; and

FIG. 29 is a plan view schematically showing part of an LED array chipin the conventional LED print head.

DETAILED DESCRIPTION OF THE INVENTION

Embodiments of the invention will now be described with reference to theattached drawings, in which like elements are indicated by likereference characters.

First Embodiment

A first embodiment of the invented semiconductor apparatus, shownschematically in perspective view in FIG. 1 and plan view in FIGS. 2 and3, is an integrated LED/driving-IC chip 100 having a substrate 101, ametal layer 102 disposed in tight contact with part of the surface ofthe substrate 101, a plurality of thin semiconductor films, referred tobelow as LED epitaxial films 103, bonded to the surface of the metallayer 102, and a thin integrated circuit film 104 bonded to the surfaceof the substrate 101, interconnected to the LED epitaxial films 103 by aplurality of individual interconnecting lines 105, which are moreexplicitly indicated in FIG. 3.

The substrate 101 may be an insulating substrate such as a glass, resin,or ceramic substrate. Alternatively, the substrate 101 may be a metalsubstrate or a semiconductor substrate.

The metal layer 102 is formed on the surface of the substrate 101 in aregion adjacent to but not overlapping the part to which the thinintegrated circuit film 104 is bonded. The metal layer 102 is, forexample, a palladium or gold film with a thickness of about one hundrednanometers (100 nm=0.1 μm). The LED epitaxial films 103 are bonded tothe surface of the metal layer 102. The functions of the metal layer 102include both bonding of the LED epitaxial films 103 and electricalconnecting of a common terminal area (not visible) on the bottom surfaceof the LED epitaxial film to a common terminal area (not visible) on thesubstrate 101. An ohmic contact is preferably formed between the metallayer 102 and the common terminal area on the substrate 101. The commonterminal areas of the LED epitaxial films 103 in this embodiment is ann-type GaAs layer that occupies the entire undersurface of the LEDepitaxial film. The common terminal area of the substrate 101 indicatesa substrate region contacting the metal layer 102 provided on thesubstrate 101.

In a modification of the first embodiment, the common terminal area ofthe substrate 101 includes terminals formed on the substrate 101, makingcontact with both the metal layer 102 and the thin integrated circuitfilm 104. In another modification, the metal layer 102 covers the entiresurface of the substrate 101 and the LED epitaxial films 103 and thinintegrated circuit film 104 are both bonded to the surface of the metallayer 102.

As shown in FIG. 3, a plurality of light-emitting diodes 106 (LEDs, alsoreferred to below as light-emitting parts or regions) are formed atregular intervals in the LED epitaxial films 103. The LEDs 106 arealigned in the longitudinal direction or X-direction of the substrate101 to form a row of LEDs with an array pitch denoted P₁ in FIG. 3. Inthe orthogonal direction or Y-direction, the LED epitaxial films 103have a width W₁ greater than the width W₂ of the light-emitting regionsor LEDs 106. For example, the LED width W₂ may be 20 μm and the width W₁of the LED epitaxial films 103 may be 50 μm, leaving a margin of 15 μmon both sides of the LEDs 106. The width W₁ of the LED epitaxial films103 is much less than a substrate thickness (typically about 400 μm) ofa conventional LED array chip having electrode pads.

The invention is not limited to a single regular row of LEDs. The LEDs106 may be disposed in two or more linear arrays offset in theY-direction, and the intervals between the LEDs 106 need not all be thesame. The number of LEDs is not restricted to the ninety-six seen inFIG. 2. The widths W₁ of the LED epitaxial films 103 and W₂ of thelight-emitting regions 105 are not limited to the values mentionedabove.

The LED epitaxial films 103 are preferably grown as an epitaxial film ona separate substrate, as will be described below, and then transferredonto the metal layer 102. The thickness of the LED epitaxial films 103may be about 2 μm, which is sufficient to obtain stable LED operatingcharacteristics (for example, light-emitting characteristics andelectrical characteristics). This thickness is much thinner than theconventional thickness (typically about 300 μm) of an LED array chiphaving electrode pads. The probability of open-circuit faults in theindividual interconnecting lines 105 increases as the thickness of theLED epitaxial films 103 and the resulting step height at their edgesincreases. To avoid the occurrence of this type of defect, the thicknessof the LED epitaxial films 103 is preferably less than 10 μm.

The thin integrated circuit film 104 is a thin semiconductor film inwhich an integrated circuit is fabricated. As shown in FIG. 3, theintegrated circuit comprises a plurality of driving circuits 107 thatdrive individual LEDs 106, the driving circuits 107 forming repeatingcircuit units in the integrated circuit. The driving circuits 107 aredisposed at regular intervals, facing the plurality of LEDs 106. Besidesthe driving circuits 107, the thin integrated circuit film 104 includesshared circuitry for illumination control of the LEDs 106. The thicknessof the thin integrated circuit film 104 is on the same order as thethickness of the LED epitaxial films 103, e.g., less than 10 μm.

In a modification of the first embodiment, a dielectric film such as apolyimide film is used to planarize the steps at the edges of the LEDepitaxial films 103 and the thin integrated circuit film 104. Thethicknesses of the LED epitaxial films 103 and the thin integratedcircuit film 104 may then be greater than 10 μm.

Referring to FIG. 3, when the LEDs 106 are disposed in a single row withan array pitch P₁, the driving circuits 107 are preferably arranged inan array extending in the same direction (the X-direction in thedrawings), with a substantially equal array pitch P₂, so that thedriving circuits 107 face the LEDs they drive.

The individual interconnecting lines 105 electrically interconnect theupper surfaces of the light-emitting regions 105 in the LED epitaxialfilms 103 with individual driving terminals 107 a in the drivingcircuits 107 on the substrate 101. The individual interconnecting lines105 may be formed by patterning a thin conductive film. Specificexamples of suitable films include a single-layer gold film, amulti-layer film with titanium, platinum, and gold layers (a Ti/Pt/Aufilm), a multi-layer film with gold and zinc layers (an Au/Zn film), amulti-layer film with a gold layer and a gold-germanium-nickel layer (anAuGeNi/Au film), a single-layer palladium film, a multi-layer film withpalladium and gold layers (a Pd/Au film), a single-layer aluminum film,a multi-layer film with aluminum and nickel layers (an Al/Ni film), apolycrystalline silicon (polysilicon) film, an indium tin oxide (ITO)film, a zinc oxide (ZnO) film, and various combinations of these films.

When the individual interconnecting lines 105 are formed from a thinfilm, since their width is restricted by the array pitch P₁ of the LEDs106, a significant voltage drop will occur if the individualinterconnecting lines 105 are too long, particularly in a dense lineararray in which the array pitch P₁ is relatively small. If severalmilliamperes of driving current must be supplied through an individualinterconnecting line 105 that is 5 μm wide and 0.5 μm thick, forexample, the length of the individual interconnecting line is preferablyless than about 200 μm.

Short circuits between the individual interconnecting lines 105 and thetop and side surfaces of the LED epitaxial films 103, the metal layer102, the surface of the substrate 101, and the driving circuits 107 areprevented by an interlayer dielectric film (the dielectric film 117shown in FIGS. 4, 6D, and 6E) that insulates the individualinterconnecting lines 105 from these regions as necessary.

Referring to FIG. 4, the LED epitaxial films 103 comprise, from thebottom up, an n-type gallium arsenide (GaAs) layer 111 and three n-typealuminum gallium arsenide (AlGaAs) layers: an Al_(x)Ga_(1-n)As lowercladding layer 112 (0≦x<1), an Al_(y)Ga_(1-y)As active layer 113(0≦y<1), and an Al_(z)Ga_(1-z)As upper cladding layer 114 (0≦z<1). Asecond n-type GaAs contact layer is formed on the n-typeAl_(z)Ga_(1-z)As layer 114 and then partially removed and partiallydoped with zinc (Zn) to create a p-type GaAs contact layer 115 for eachLED. Each LED also includes a p-type zinc diffusion region 116 formed inthe n-type Al_(y)Ga_(1-y)As active layer 113 and n-type Al_(z)Ga_(1-z)Asupper cladding layer 114. Light is emitted when forward current issupplied across the pn junction at the interface between the p-type andn-type regions. The part of the second GaAs layer including the pnjunction is removed, leaving the p-type GaAs contact layer 115 as anisland within each LED. The part of the n-type Al_(z)Ga_(1-z)As uppercladding layer 114 including the pn junction is covered by thedielectric film 117 mentioned above, which may be considered as part ofthe LED epitaxial film 103.

The n-type GaAs layer 111 is about 10 nm (0.01 μm) thick, the n-typeAl_(x)Ga_(1-x)As lower cladding layer 112 is about 0.5 μm thick, then-type Al_(y)Ga_(1-y)As active layer 113 is about 1 μm thick, the n-typeAl_(z)Ga_(1-z)As upper cladding layer 114 is about 0.5 μm thick, and thep-type GaAs contact layer 115 a about 10 nm (0.01 μm) thick. The totalthickness of the LED epitaxial film 103 is about 2.02 μm.

The aluminum composition ratios x, y, z of the AlGaAs layers arepreferably selected so that x>y and z>y (e.g., x=z=0.4, y=0.1), and thediffusion front of the zinc diffusion region 116 is preferably locatedwithin the n-type Al_(y)Ga_(1-y)As active layer active 113. With thisstructure, minority carriers injected through the pn junction areconfined within the n-type Al_(y)Ga_(1-y)As active layer 113 and thep-type Al_(y)Ga_(1-y)As region created therein by zinc diffusion, sothat high luminous efficiency is obtained. The structure shown in FIG. 4enables high luminous efficiency to be obtained with an LED epitaxialfilm 103 as thin as about 2 μm.

The LED epitaxial film 103 is not limited to the thicknesses ormaterials given above. Other materials, such as aluminum-gallium indiumphosphide ((Al_(x)Ga_(1-x))_(y)In_(1-y)P, where 0≦x<1 and 0≦y<1),gallium nitride (GaN), aluminum gallium nitride (AlGaN), and indiumgallium nitride (InGaN) may also be employed. The LED shown in FIG. 4has a double hetero-junction structure, but it is also possible tofabricate LEDs with a single hetero-junction structure or a homojunctionstructure, by forming a diffusion region in an epitaxial layer of thesingle hetero-multilayer type or the single-layer type.

Next, a method of fabricating the integrated LED/driving-IC chip 100will be described. In this method, a plurality of integratedLED/driving-IC chips are formed simultaneously on a wafer substrate 101a as shown in FIG. 5. Steps in the fabrication process are illustratedin FIGS. 6A to 6E, which show part of one integrated LED/driving-ICchip.

In the fabrication process, first a layer of metal is deposited on thewafer substrate 101 a and patterned by lift-off, for example, to leave ametal layer 102 in each chip formation area 101 a. LED epitaxial films103 are then bonded to each metal layer 102 and the thin integratedcircuit film 104 is bonded to the substrate 101 a in each chip formationarea 101 b, as shown in FIG. 6B. The LED epitaxial films 103 and thinintegrated circuit films 104 may be bonded in either order. A dielectricfilm 117 is then formed so as to cover necessary parts of the substrate101 a, metal layers 102, LED epitaxial films 103, and thin integratedcircuit films 104, as shown in FIG. 6C. The individual interconnectinglines 105 are formed on the dielectric film 117 as shown in FIG. 6D, byphotolithography. The wafer substrate 101 a is then diced along dicinglines 118 shown in FIG. 5 and separated into individual integratedLED/driving-IC chips 100, as shown in FIG. 6E.

The area covered by the dielectric film 117 need not be the area shownin these drawings. For example, the dielectric film 117 can be formed soas to cover only the LED epitaxial films 103 and metal layer 102.

To form ohmic contacts between the metal layer 102 and the commonterminal area (not visible) on the underside of the LED epitaxial films103, and between the metal layer 102 and the common terminal area (notvisible) on the substrate 101, after the LED epitaxial films 103 havebeen placed in tight contact with the metal layer 102, the wafer isannealed at a temperature of 200° C. to 250° C. This annealing alsostrengthens the bonds between the LED epitaxial films 103 and the metallayer 102. Similarly, after the individual interconnecting lines 105have been formed by photolithography, the wafer is annealed at atemperature of about 200° C. to form ohmic contacts.

Next, a fabrication process for the LED epitaxial films 103 will bedescribed with reference to FIGS. 7 to 10. The illustrated processsimultaneously creates a plurality of LED epitaxial films 103 forbonding to a plurality of integrated LED/driving-IC chips 100.

Referring to FIG. 7, the fabrication process begins with the formationof an LED epitaxial layer 103 a on a fabrication substrate 120 bywell-known techniques such as metal organic chemical vapor deposition(MOCVD) or molecular beam epitaxy (MBE). The LED epitaxial filmfabrication substrate 120 in FIG. 7 includes a GaAs substrate 121, aGaAs buffer layer 122, an aluminum-gallium indium phosphide ((AlGa)InP)etching stop layer 123, and an aluminum arsenide (AlAs) sacrificiallayer 124. The n-type GaAs contact layer 111, n-type Al_(x)Ga_(1-x)Aslower cladding layer 112, n-type Al_(y)Ga_(1-y)As active layer 113,n-type Al_(z)Ga_(1-z)As upper cladding layer 114, and n-type GaAscontact layer 115 a are formed in this order on the AlAs sacrificiallayer 124, creating the LED epitaxial layer 103 a.

The structure shown in FIG. 7 is capable of modification. Various layersmay be added, for example, and the etching stop layer 123 may be omittedif it is not needed.

Referring to FIG. 8, an interlayer dielectric film 117 a is now formed,openings are created therein, and a p-type impurity comprising zinc (Zn)is diffused through the appropriate openings by, for example, asolid-phase diffusion method to create the zinc diffusion regions 116.The diffusion source film (not shown) used for the solid-phase diffusionprocess is then removed to expose the surface of the GaAs contact layerin the zinc diffusion regions 116. Due to the p-type impurity diffusion,the n-type GaAs contact layer 115 a has become a p-type GaAs contactlayer 115 in these regions. The part of the GaAs contact layer includingthe pn junction is preferably removed by etching, as shown in FIG. 8.

Referring FIGS. 9 and 10, the LED epitaxial films are now lifted offfrom the fabrication substrate 120. Parallel trenches 125 are formed inthe LED epitaxial layer 103 a by photolithography and etching. Forsimplicity, the photoresist mask used in these processes is not shown inthe drawings, and only one trench 125 is shown (in FIG. 10). The etchantis a solution of phosphoric acid and hydrogen peroxide, which etches theAlGaAs layers 112, 113, 114 and GaAs layers 111, 115, much faster than(AlGa)InP etching stop layer 123. Therefore etching to form the trench125 stops at the surface of the etching stop layer 123. When the trench125 is formed, part of the surface of the sacrificial layer 124 shouldbe exposed to the etchant. Although the phosphoric acid/hydrogenperoxide solution does not necessarily etch the interlayer dielectricfilm 117 a, the interlayer dielectric film 117 a is removed from theareas in which the trenches 125 will be etched. The same photoresistmask can be used for removing the dielectric film 117 a from these areasand for etching the trenches 125. The (AlGa)InP etching stop layer 123ensures that the trench etching process does not excavate the GaAssubstrate 121.

FIG. 9, which shows a cross section through line S₉-S₉ in FIG. 10, givesa side view of what will become one LED epitaxial film 103. FIG. 10shows end sectional views of what will become two LED epitaxial films103. The interval between trenches 125 defines the LED epitaxial filmwidth denoted W₁ in FIG. 3. To enable the fabrication of thin LEDepitaxial films and to enable them to be separated from the LEDepitaxial film fabrication substrate 120 in a relatively short time, thewidth W₁ is preferably less than 300 μm. A small width W₁ (such as the50-μm width mentioned earlier) also increases the number of LEDepitaxial films that can be formed simultaneously, thereby reducing thematerial cost and total fabrication cost of each LED epitaxial film.

Referring to FIGS. 9 and 10, after the formation of trenches 125, theAlAs sacrificial layer 124 is selectively etched with ,for example, a10% hydrofluoric acid (HF) solution. Since the HF etching rate of theAlAs layer 124 is much faster than that of the AlGaAs layers 112 to 114,the GaAs layers 111, 115, 121, and 122 and the (AlGa)InP etching stoplayer 123, the AlAs sacrificial layer 124 can be etched withoutsignificant damage to these other layers. FIG. 10 shows an intermediatestage in the etching process, in which part of the AlAs sacrificiallayer 124 still remains. By the end of the etching process, the AlAssacrificial layer 124 is completely removed, as shown in FIG. 9,enabling the LED epitaxial films 103 to be detached from the fabricationsubstrate 120.

After the AlAs sacrificial layer 124 has been completely removed byetching, the LED epitaxial films 103 are cleansed with deionized waterso that no etching solution residue remains. Then each LED epitaxialfilm 103 is lifted from the fabrication substrate 120 by, for example, avacuum suction jig, transferred to the metal layer 102 on the substrate101, and bonded thereto as explained above.

To protect the LED epitaxial films 103 during the etching processes andfacilitate their handling during the separation and attachmentprocesses, a protective supporting layer (not shown) may be formed onthe LED epitaxial layer 103 a before formation of the trenches 125, andremoved from the LED epitaxial films 103 after they have been bonded tothe metal layer 102.

Next, the fabrication of the thin integrated circuit film 104 will bedescribed with reference to FIGS. 11A to 11C. In the process described,the thin integrated circuit film 104 is fabricated on asilicon-on-insulator (SOI) substrate 130 comprising a silicon substrate131, a buried oxide layer 132, and a semiconductor silicon layer 133.The buried oxide layer 132 is a silicon dioxide (SiO₂) layer, alsoreferred to as a BOX layer. The semiconductor silicon layer 133 is alsoreferred to as an SOI layer. In FIG. 11A, an integrated circuit 133 a isformed near the surface of the semiconductor silicon layer 133. Next, asshown in FIG. 11B, the SiO₂ layer 132 is selectively etched with, forexample, HF. FIG. 11B shows an intermediate stage in the etchingprocess; when the etching process ends, the SiO₂ layer 132 is completelyremoved. The semiconductor silicon layer 133, including the integratedcircuit 133 a, is now lifted from the silicon substrate 131 by, forexample, a vacuum suction jig, transferred to the desired location onthe wafer substrate 101 a, and attached to the wafer substrate 101 a asa thin integrated circuit film 104, as shown in FIG. 11C.

To protect the integrated circuit 133 a during the etching of the SiO₂layer 132, and to facilitate the handling of the thin integrated circuitfilm 104 during the separation and attachment processes, a protectivesupporting layer (not shown) may be formed on the semiconductor siliconlayer 133 before the etching process shown in FIG. 11B, and removedafter the attachment process shown in FIG. 11C.

One effect of the first embodiment is that since the LED epitaxial films103 are electrically connected to the driving circuits 107 in the thinintegrated circuit film 104 by thin-film individual interconnectinglines 105, no wire-bonding connections have to be made between the LEDepitaxial films 103 and the driving circuits 107. Assembly costs cantherefore be reduced, and the rate of occurrence of interconnectionfaults is reduced.

A related effect is that the area occupied by the LED epitaxial films103 can be much smaller than the area occupied by a conventional LEDarray chip, and the area occupied by the thin integrated circuit film104 can also be reduced, because no wire bonding pads need be providedfor interconnections between the two. Furthermore, since the LEDepitaxial films 103 are supported by the substrate 101 and need not bethickened to provide strength for wire bonding, they can be much thinnerthan conventional LED array chips. These effects lead to a substantialreduction in material costs. In particular, the necessary amount ofrelatively expensive compound semiconductor materials such as galliumarsenide can be greatly reduced, as compared with conventional LED arraychips, even when the fabrication substrate 120 is taken into account.

A further effect is that, since the LEDs 106 in the LED epitaxial films103 are close to their driving circuits 107, the individualinterconnecting lines 105 can be correspondingly short, leading to areduction in electrical resistance, not to mention an overall reductionin the combined width of the apparatus including the LEDs and theirdriving circuits. The integrated LED/driving-IC chip 100 thus takes upless space and can operate on less power than a conventional paired LEDarray chip and driver IC chip.

Furthermore, in the integrated LED/driving-IC chip 100 of the firstembodiment, the metal layer 103 is disposed below the epitaxial film104, and the epitaxial film 104 has an extremely thin thickness, forexample, a thickness of about 2 μm. Accordingly, not only light isdirectly emitted upward from the LED 105 but also light emitted downwardfrom the LED 105 is reflected by a surface of the metal layer 103 totravel upward through the epitaxial film 104. Therefore, luminousintensity of the integrated LED/driving-IC chip 100 can be increased.

Second Embodiment

A second embodiment of the invented semiconductor apparatus is shownschematically in partial plan view in FIG. 12. This integratedLED/driving-IC chip 150 differs from the integrated LED/driving-IC chip100 in the first embodiment in that relay terminal areas 151 comprisinga conductive material are provided on the substrate 101 between the LEDepitaxial films 103 and the thin integrated circuit film 104. Theindividual interconnecting lines 105 extend from above thelight-emitting parts of the LEDs 106 in the LED epitaxial films 103 tothe relay terminal areas 151 on the substrate 101, then to theindividual terminal areas 107 a of the thin integrated circuit film 104.The relay terminal areas 151 make it possible to change the positionalrelationship between the LED epitaxial films 103 and thin integratedcircuit film 104: for example, to separate them by a greater distance,as illustrated by a comparison of FIGS. 3 and 12.

Except for the foregoing point, the second embodiment is identical tothe first embodiment described above.

Third Embodiment

A third embodiment of the invented semiconductor apparatus is shownschematically in partial plan view in FIG. 13 and in partial crosssectional view in FIG. 14. This integrated LED/driving-IC chip 160differs from the integrated LED/driving-IC chip 100 in the firstembodiment in that there is no metal layer between the LED epitaxialfilms 103 and the substrate 101. The upper surface of the substrate 101and lower surface of the LED epitaxial films 103 are treated by anappropriate chemical method to remove contaminants and provideplanarization to, for example, the order of one atomic layer, afterwhich these two surfaces are placed in tight contact and bonded togetherby the application of pressure and heat.

Although the heating temperature necessary to achieve secure bonding ishigher in the second embodiment than in the first embodiment, the secondembodiment eliminates the possibility of bonding defects caused bythickness irregularities in the metal layer interposed between the LEDepitaxial films and the substrate in the first embodiment. The alignmentaccuracy between the array of LEDs 106 and the array of driving circuits107 can also be improved, because the error associated with theinterposed metal layer is eliminated.

Aside from the absence of the metal layer, the third embodiment isidentical to the first embodiment.

Fourth Embodiment

A fourth embodiment of the invented semiconductor apparatus is shownschematically in partial plan view in FIG. 15, partial perspective viewin FIG. 16, and partial cross sectional view in FIG. 17. In thisintegrated LED/driving-IC chip 170, each LED is formed as a separate LEDepitaxial film 171.

Each LED epitaxial film 171 has the structure shown in FIG. 17,comprising a p-type GaAs lower contact layer 172, a p-typeAl_(x)Ga_(1-x)As lower cladding layer 173, a p-type Al_(y)Ga_(1-y)Asactive layer 174, an n-type Al_(z)Ga_(1-z)As upper cladding layer 175,and an n-type GaAs upper contact layer 176. The Al composition ratios x,y, z may satisfy the conditions x>y and z>y (for example, x=z=0.4,y=0.1). A dielectric film 177 is formed on the n-type GaAs upper contactlayer 176. A central stripe of the dielectric film 177 is removed toallow the individual interconnecting line 105 to make contact with thesurface of the n-type GaAs upper contact layer 176 across the entirewidth of the LED epitaxial film 171 in the direction perpendicular tothe drawing sheet in FIG. 17. The individual interconnecting line 105extends to the terminal region 107 a of the corresponding drivingcircuit 107, as shown in FIGS. 15 and 16.

The LED epitaxial film 171 is not limited to the sectional structureshown in FIG. 17 or the composition ratios described above. Variousmodifications are possible.

One effect of the fourth embodiment is that, since each LED epitaxialfilm 171 is extremely small, temperature-induced internal stress in theLED epitaxial film, which becomes significant if the thermal expansioncoefficient of the LED epitaxial film differs greatly from that of thesubstrate 101, is greatly reduced, and one of the factors that can leadto LED failure is substantially eliminated. The reliability of theintegrated LED/driving-IC chip 170 is enhanced accordingly.

The small size of the LED epitaxial films 171 also facilitates theprocess of bonding them to the metal layer 102, since the bonding areaof each LED epitaxial film 171 is small. The rate of occurrence ofincomplete contact defects is thus reduced.

A further effect is that, since the LED epitaxial films 171 do notinclude any parts other than the light-emitting region, the width of theLED epitaxial films can be reduced and the length of the individualinterconnecting lines 105 can be correspondingly reduced.

Except for the foregoing points, the fourth embodiment is identical tothe first embodiment.

Fifth Embodiment

A fifth embodiment of the invented semiconductor apparatus is shownschematically in partial perspective view in FIG. 18 and partial planview in FIG. 19. The integrated LED/driving-IC chip 180 in the fifthembodiment comprises: a substrate 181 on which a circuit pattern 182with terminal areas 182 a is formed; a plurality of LED epitaxial films183 bonded to the surface of the substrate 181; a plurality of thinintegrated circuit films 184 bonded to the surface of the substrate 181;and a plurality of thin-film individual interconnecting lines 185 and186 (shown in FIG. 19). In the fifth embodiment, each thin integratedcircuit film 184 faces one LED epitaxial film 183, as shown in FIG. 18,and has terminal areas 184 a and 184 b, as shown in FIG. 19.

The first thin-film individual interconnecting lines 185 extend from theLEDs 106 in the LED epitaxial films 183, over the surface of thesubstrate 181, to the thin integrated circuit films 184, electricallyinterconnecting the light-emitting parts of the LEDs 106 and the facingterminal areas 184 a in the thin integrated circuit films 184. Aninterlayer dielectric layer (not shown) is provided below the firstindividual interconnecting lines 185 where necessary to avoid electricalshort circuits.

The second thin-film individual interconnecting lines 186 extend fromthe thin integrated circuit films 184 to the circuit pattern 182 on thesubstrate 181, electrically interconnecting terminal areas 184 b in thethin integrated circuit films 184 and the terminal areas 182 a of thecircuit pattern 182. These individual interconnecting lines 186 are usedfor, for example, input and output of electrical signals and power forthe driving circuits in the thin integrated circuit films 184. Aninterlayer dielectric layer (not shown) is provided below the secondindividual interconnecting lines 186 where necessary to avoid electricalshort circuits with the circuit pattern 182 and thin integrated circuitfilms 184.

Since the conventional bonding wires are replaced by thin-filmindividual interconnecting lines 185 and 186, a reduction in size andmaterial can be achieved, and the rate of interconnection faults can bereduced. Compared with the first embodiment, the reduced size of thethin integrated circuit films 184 facilitates their attachment to thesubstrate.

Except for the foregoing points, the fifth embodiment is identical tothe first embodiment.

Sixth Embodiment

A sixth embodiment of the invented semiconductor apparatus is shownschematically in partial plan view in FIG. 20. The integratedLED/driving-IC chip 190 according to the sixth embodiment comprises: asubstrate 191 on which a circuit pattern 192 is formed; a plurality ofLED epitaxial films 193 bonded to the surface of the substrate 191; aplurality of thin integrated circuit films 194 bonded to the surface ofthe substrate 191; and a plurality of thin-film individualinterconnecting lines 195 and 196. The sixth embodiment differs from thefifth embodiment in that each thin integrated circuit film 194 facesthree LED epitaxial films 193. The thin integrated circuit films 194have terminal areas to which the first and second individualinterconnecting lines 195 and 196 are connected. The circuit pattern 192on the substrate 191 has terminal areas to which the second individualinterconnecting lines 196 are connected.

The first thin-film individual interconnecting lines 195 extend from theLEDs in the LED epitaxial films 193, over the surface of the substrate191, to the thin integrated circuit films 194, electricallyinterconnecting the light-emitting parts of the LEDs and the facingterminal areas in the thin integrated circuit films 194. An interlayerdielectric layer (not shown) is provided below the first individualinterconnecting lines 195 where necessary to avoid electrical shortcircuits.

The second thin-film individual interconnecting lines 196 extend fromthe thin integrated circuit films 194 to the terminal areas of thecircuit pattern 192 in the substrate 191, electrically interconnectingterminal areas in the thin integrated circuit films 194 with theterminal areas of the circuit pattern 192. The second individualinterconnecting lines 196 are used for, for example, input and output ofelectrical signals and power for the driving circuits in the thinintegrated circuit films 194. An interlayer dielectric layer (not shown)is provided below the second individual interconnecting lines 196 wherenecessary to avoid electrical short circuits with the circuit pattern192 and thin integrated circuit films 194.

Compared with the fifth embodiment, the sixth embodiment requires fewersecond individual interconnecting lines, since there are fewer thinintegrated circuit films, and the circuit pattern on the substrate canbe simplified accordingly.

In other respects, the sixth embodiment is substantially identical tothe fifth embodiment. Since the conventional bonding wires are replacedby thin-film individual interconnecting lines 195 and 196, a reductionin size and material can be achieved, and the rate of interconnectionfaults can be reduced.

Seventh Embodiment

A seventh embodiment of the invented semiconductor apparatus is shownschematically in partial plan view in FIG. 21. The integratedLED/driving-IC chip 200 according to the seventh embodiment comprises: asubstrate 201 on which a circuit pattern 202 with terminal areas 202 ais formed; a metal layer 201 a formed on the substrate 201 in tightcontact therewith; a plurality of LED epitaxial films 203 bonded to thesurface of the metal layer 201 a; a thin integrated circuit film 204bonded to the surface of the substrate 201; and a plurality of thin-filmindividual interconnecting lines 205 and 206. The thin integratedcircuit film 204 has terminal areas 204 a and 204 b. The integratedLED/driving-IC chip 200 according to the seventh embodiment differs fromthe integrated LED/driving-IC chip 180 shown in FIG. 18 (the fifthembodiment) in that each LED 106 is formed as a separate LED epitaxialfilm 203. The LED epitaxial films 203 are bonded onto the metal layer201 a in a single row at regular intervals.

The circuit pattern 202 is an interconnection pattern connectinginput/output terminals for power and electrical signals on the substrate201 with terminal areas 204 b of the thin integrated circuit film 204,and with terminals of other circuit elements such as resistors,capacitors, and memory circuits, external to the thin integrated circuitfilm 204, which are provided on the substrate 201 for driving control.The circuit pattern 202 may also connect terminal areas 204 b of thethin integrated circuit film 204 with the terminals of these resistors,capacitors, memory circuits, and other circuit elements.

The first individual interconnecting lines 205 extend from above theLEDs in the LED epitaxial film 203, over the surface of the substrate201, to the thin integrated circuit film 204, electricallyinterconnecting the light-emitting parts of the LEDs and the facingterminal areas 204 a in the thin integrated circuit film 204. Aninterlayer dielectric film (not shown) is provided below the individualinterconnecting lines 205 where necessary to avoid electrical shortcircuits.

The second individual interconnecting lines 206 extend from the thinintegrated circuit film 204 to the circuit pattern 202 on the substrate201, electrically interconnecting terminal areas 204 b in the thinintegrated circuit film 204 and terminal areas 202 a of the circuitpattern 202. The second individual interconnecting lines 206 are usedfor, for example, input and output of electrical signals and power forthe driving circuits in the thin integrated circuit film 204. Aninterlayer dielectric layer (not shown) is provided below the individualinterconnecting lines 206 where necessary to avoid electrical shortcircuits with the circuit pattern 202 or thin integrated circuit film204.

Except for the foregoing points, the seventh embodiment is identical tothe fifth embodiment described above. Since the conventional bondingwires are replaced by thin-film individual interconnecting lines 205 and206, a reduction in size and material can be achieved, and the rate ofinterconnection faults can be reduced. In addition, the small size ofthe LED epitaxial films 203 facilitates their secure bonding to themetal layer 201 a, enables the width of the LED epitaxial films to bereduced, and reduces the LED failure rate by reducing thermal stress.

Eighth Embodiment

An eighth embodiment of the invented semiconductor apparatus is shownschematically in plan view in FIG. 22 and in partial perspective view inFIG. 23. The integrated LED/driving-IC chip 210 in the eighth embodimentcomprises: a substrate 211 on which a circuit pattern 212 is formed; ametal layer 211 a formed on the substrate 211 in tight contacttherewith; a plurality of LED epitaxial films 213 bonded to the surfaceof the metal layer 211 a; a thin integrated circuit film 214 bonded tothe surface of the substrate 211; and a plurality of thin-filmindividual interconnecting lines 215 and 216. The LED epitaxial films213 are bonded onto the metal layer 211 a in a single row. Terminalareas for the individual interconnecting lines 215 and 216 are providedin the thin integrated circuit film 214, and terminal areas for thesecond individual interconnecting lines 216 are provided in the circuitpattern 212 on the substrate 211.

The first thin-film individual interconnecting lines 215 extend fromabove the LEDs in the LED epitaxial films 213, over the surface of thesubstrate 211, to the thin integrated circuit film 214, electricallyinterconnecting the light-emitting parts of the LEDs and the facingterminal areas in the thin integrated circuit film 214. An interlayerdielectric film (not shown) is provided below the individualinterconnecting lines 215 where necessary to avoid electrical shortcircuits.

The second thin-film individual interconnecting lines 216 extend fromthe thin integrated circuit film 214 to the circuit pattern 212 on thesubstrate 211, electrically interconnecting terminal areas in the thinintegrated circuit film 214 and terminal areas of the circuit pattern212. The second individual interconnecting lines 216 are used for, forexample, input and output of electrical signals and power for thedriving circuits in the thin integrated circuit film 214. An interlayerdielectric layer (not shown) is provided below the individualinterconnecting lines 216 where necessary to avoid electrical shortcircuits with the circuit pattern 212 and thin integrated circuit film214.

Since the conventional bonding wires are replaced by thin-filmindividual interconnecting lines 215 and 216, a reduction in size andmaterial can be achieved, and the rate of interconnection faults can bereduced.

A fabrication process for the thin integrated circuit film 214 in theeighth embodiment is illustrated schematically in FIG. 24. A pluralityof thin integrated circuit films 214 are formed together on afabrication substrate 217 such as, for example, a glass substrate. Eachthin integrated circuit film 214 is detached from the glass substrate217, and then bonded to the substrate 211 of an integratedLED/driving-IC chip 210. The fabrication process includes heat treatmentsteps, but since these steps are carried out on the glass substrate 217,the substrate 211 of the integrated LED/driving-IC chip 210 need not behighly heat resistant, which widens the choice of substrate materials.

Except for the foregoing points, the eighth embodiment is similar to thefirst embodiment.

Ninth Embodiment

A ninth embodiment of the invented semiconductor apparatus is shownschematically in plan view in FIG. 25. The integrated LED/driving-ICchip 220 according to the ninth embodiment comprises: a substrate 221 onwhich a circuit pattern 222 is formed; a metal layer 221 a formed on thesubstrate 221 in tight contact therewith; a plurality of LED epitaxialfilms 223 bonded to the surface of the metal layer 221 a; a pair of thinintegrated circuit films 224 bonded to the surface of the substrate 221;and a plurality of thin-film individual interconnecting lines 225 and226. The LED epitaxial films 223 are bonded onto the metal layer 221 ain a single row. The thin integrated circuit films 224 have terminalareas for the first and second individual interconnecting lines 225 and226, and the circuit pattern 222 on the substrate 221 has terminal areasfor the second individual interconnecting lines 226.

The number of LED epitaxial films 223 is not limited to the eight shownin the drawings, and the number of thin integrated circuit films 224 isnot limited to two. For example, there may be three or more thinintegrated circuit films 224.

The first thin-film individual interconnecting lines 225 extend from theLED epitaxial films 223 over the surface of the substrate 221 to thethin integrated circuit films 224, electrically interconnecting thelight-emitting parts of the LEDs in the LED epitaxial films 223 withterminal areas in the thin integrated circuit film 224. An interlayerdielectric film (not shown) is provided below the individualinterconnecting lines 225 where necessary to avoid electrical shortcircuits.

The second thin-film individual interconnecting lines 226 extend fromthe thin integrated circuit films 224 to the circuit pattern 222 on thesubstrate 221, electrically interconnecting terminal areas in the thinintegrated circuit films 224 with terminal areas of the circuit pattern222. The second individual interconnecting lines 226 are used for, forexample, input and output of electrical signals and power for thedriving circuits in the thin integrated circuit films 224. An interlayerdielectric film (not shown) is provided below the individualinterconnecting lines 226 where necessary to avoid electrical shortcircuits with the circuit pattern 222 and thin integrated circuit films224.

Except for the division of the thin integrated circuit film intomultiple parts, the ninth embodiment is similar to the eighthembodiment. Since the conventional bonding wires are replaced bythin-film individual interconnecting lines 225 and 226, a reduction insize and material can be achieved, and the rate of interconnectionfaults can be reduced. The division of the thin integrated circuit filminto multiple parts facilitates the handling and attachment thereof.

LED Print Head

FIG. 26 shows an example of an LED print head 700 employing the presentinvention. The LED print head 700 includes a base 701 on which an LEDunit 702 is mounted. The LED unit 702 includes a plurality of integratedLED/driving-IC chips 702 a of the type described in any of the precedingembodiments, mounted so that their light-emitting parts are positionedbeneath a rod lens array 703. The rod lens array 703 is supported by aholder 704. The base 701, LED unit 702, and holder 704 are held togetherby clamps 705. Light emitted by the light-emitting elements in the LEDunit 702 is focused by rod lenses in the rod lens array 703 onto, forexample, a photosensitive drum (not shown) in an electrophotographicprinter or copier.

Use of integrated LED/driving-IC chips 702 a instead of the conventionalpaired LED array chips and driver IC chips enables the LED unit 702 tobe reduced in size and reduces its assembly cost, as there are fewerchips to be mounted.

LED Printer

FIG. 27 shows an example of a full-color LED printer 800 in which thepresent invention may be employed. The printer 800 has a yellow (Y)process unit 801, a magenta (M) process unit 802, a cyan (C) processunit 803, and a black (K) process unit 804, which are mounted followingone another in tandem fashion. The cyan process unit 803, for example,includes a photosensitive drum 803 a that turns in the directionindicated by the arrow, a charging unit 803 b that supplies current tothe photosensitive drum 803 a to charge the surface thereof, an LEDprint head 803 c that selectively illuminates the charged surface of thephotosensitive drum 803 a to form an electrostatic latent image, adeveloping unit 803 d that supplies cyan toner particles to the surfaceof the photosensitive drum 803 a to develop the electrostatic latentimage, and a cleaning unit 803 e that removes remaining toner from thephotosensitive drum 803 a after the developed image has been transferredto paper. The LED print head 803 c has, for example, the structure shownin FIG. 26, including integrated LED/driving-IC chips 702 a of the typedescribed in any of the nine embodiments above. The other process units801, 802, 804 are similar in structure to the cyan process unit 803, butuse different toner colors.

The paper 805 (or other media) is held as a stack of sheets in acassette 806. A hopping roller 807 feeds the paper 805 one sheet at atime toward a paired transport roller 810 and pinch roller 808. Afterpassing between these rollers, the paper 805 travels to a registrationroller 811 and pinch roller 809, which feed the paper toward the yellowprocess unit 801.

The paper 810 passes through the process units 801, 802, 803, 804 inturn, traveling in each process unit between the photosensitive drum anda transfer roller 812 made of, for example, semi-conductive rubber. Thetransfer roller 812 is charged so as to create a potential differencebetween it and the photosensitive drum. The potential differenceattracts the toner image from the photosensitive drum onto the paper805. A full-color image is built up on the paper 805 in four stages, theyellow process unit 801 printing a yellow image, the magenta processunit 802 a magenta image, the cyan process unit 803 a cyan image, andthe black process unit 804 a black image.

From the black process unit 804, the paper 805 travels through a fuser813, in which a heat roller and back-up roller apply heat and pressureto fuse the transferred toner image onto the paper. A first deliveryroller 814 and pinch roller 816 then feed the paper 805 upward to asecond delivery roller 815 and pinch roller 817, which deliver theprinted paper onto a stacker 818 at the top of the printer.

The photosensitive drums and various of the rollers are driven by motorsand gears not shown in the drawing. The motors are controlled by acontrol unit (not shown) that, for example, drives the transport roller810 and halts the registration roller 811 until the front edge of asheet of paper 805 rests flush against registration roller 811, thendrives the registration roller 811, thereby assuring that the paper 805is correctly aligned during its travel through the process units 801,802, 803, 804. The transport roller 810, registration roller 811,delivery rollers 814, 815, and pinch rollers 808, 809, 816, 817 alsohave the function of changing the direction of travel of the paper 805.

The LED heads account for a significant part of the manufacturing costof this type of LED printer 800. By using highly reliable andspace-efficient integrated LED/driving-IC chips and enabling these chipsand the LED units in the LED heads to be manufactured by a simplifiedfabrication process with reduced material costs, the present inventionenables a high-quality printer to be produced at a comparatively lowcost.

Similar advantages are obtainable if the invention is applied to afull-color copier. The invention can also be advantageously used in amonochrome printer or copier or a multiple-color printer or copier, butits effect is particularly great in a full-color image-forming apparatus(printer or copier), because of the large number of exposure devices(print heads) required in such apparatus.

The invention is not limited to the preceding embodiments. For example,the metal layer 102 used in several of the embodiments can be replacedby a thin film of polysilicon or any other suitable material.

The metal layer 102 has been drawn as a rectangle with straight edgesand square corners, but the rectangular shape can be modified toinclude, for example, a cut-off corner and a side meander. The cut-offcorner can be used as a reference for determining the orientation of thechip. The meander can be used as a reference for determining thepositions of the LEDs.

The LED epitaxial films may be replaced with a thin semiconductor filmin which semiconductor devices other than LEDs are formed. Possibleexamples of these other semiconductor devices include semiconductorlasers, photodetectors, Hall elements, and piezoelectric devices.

The LED epitaxial films need not be grown as an epitaxial layer on afabrication substrate. Any available fabrication method may be used.

The LED epitaxial films need not be mounted adjacent to the thinintegrated circuit film on the substrate; it may be separated from thethin integrated circuit film by an arbitrary distance, provided voltagedrop in the interconnecting lines does not become a problem.

The thin integrated circuit film has been described as being fabricatedon an SOI substrate, but other fabrication methods can be used. Forexample, the thin integrated circuit film may be a polysilicon film withthin-film transistors (TFTs). To fabricate this type of film, a thinamorphous silicon film may be formed by a method such as chemical vapordeposition (CVD), with a relatively low deposition temperature, on aglass substrate on which an SiO₂ layer several hundred nanometers thickhas been formed. The amorphous silicon is then recrystallized by, forexample, illumination by an excimer pulse laser to obtain apolycrystalline silicon layer. Integrated circuit patterns includingcircuit elements such as transistors are formed in the polycrystallinesilicon layer.

The common electrode formed on the underside of the LED epitaxial filmsmay be divided into multiple electrodes, to drive different groups ofLEDs at different timings.

Those skilled in the art will recognize that further variations arepossible within the scope of invention, which is defined by the appendedclaims.

1-27. (canceled)
 28. A combined semiconductor apparatus comprising: asubstrate having a first terminal area on an upper surface of thesubstrate; a thin semiconductor silicon film which is disposed on andbonded to the upper surface of the substrate, the thin semiconductorfilm including an integrated circuit, the thin semiconductor film havinga second terminal area on an upper surface of the thin semiconductorfilm; and at least one interconnecting line formed as a thin conductivefilm extending from the first terminal area to the second terminal areavia the upper surface of the substrate and the upper surface of the thinsemiconductor silicon film, thereby electrically connecting the firstterminal area and the second terminal area.
 29. A method of fabricatinga combined semiconductor apparatus comprising the steps of: forming asubstrate including a silicon substrate, a buried SiO₂ layer disposed onthe silicon substrate, and a silicon film disposed on the buried SiO₂layer; forming an integrated circuit in the silicon film; removing theburied SiO₂ layer with etching liquid and peeling off the silicon filmfrom the silicon substrate; and attaching the silicon film to a desiredlocation of another substrate.